Routing algorithms are the core technology of an Internet network layer, which mainly solves the problem of how to select an appropriate path and an appropriate router to forward data in an IP network. The current routing algorithms are divided into an active routing algorithm (a table-driven routing protocol) and on-demand routing (a reactive routing protocol).
Active routing protocol: an active routing discovery strategy is similar to the traditional routing protocol, that is, each node of the network should periodically send the latest routing information to other nodes, and each node should maintain one or more routing tables to store the routing information. When a network topological structure changes, the node will broadcast routing update information in the whole network, and thus each node can continuously acquire network information. Representative protocols of the active routing protocol include DSDV (Destination-Sequenced Distance. Vector, destination-sequenced distance vector), HSR (Hierarchical State Routing, hierarchical state routing), and the like; and on-demand routing protocol: unlike the active routing protocol, the on-demand routing is created by a source node only when the routing is required, so the topological structure and routing table contents are established according to demands, and may be only a part of the entire topological structure information. The routing is maintained in a communication process and is not maintained anymore after the communication is completed. The representative protocols thereof include: a DSR (dynamic source routing protocol), an AODV (Ad hoc on-demand distance vector routing protocol), a TORA (temporally ordered routing algorithm).
In these current routing algorithms, the routing problem of a distributed system is usually processed, that is, there is no centralized control node between routers to uniformly maintain and process the routing tables.
In a direct communication network (D2D, Device to Device), the network topological structure changes, and terminals in the direct communication network work under the centralized control (or partial control) of a telecommunication network. Therefore, related routing discovery and routing maintenance mechanisms in the routing algorithm need to be changed correspondingly to adapt to data relay node and path selection of a D2D data sharing network.
As shown in FIG. 1, a possible topological structure in the D2D data sharing network is represented. UEs (terminals) A, B are a data source UE and a data destination receiving UE respectively; and UEs C, D, E are potential data relay UEs.
The channel states between the UEs can be acquired by initiating a Discovery flow between the UEs or measuring pilot frequency. It can be seen from FIG. 1 that, according to a channel detection result, a link C-to-B has worse quality, and thus cannot establish direct communication. Links A-to-C, A-to-D, D-to-E, E-to-B meet the requirements of the direct communication, and thus can establish the direct communication.
If the aforementioned selection of an available path and a relay node is completed according to the “on-demand routing protocol” algorithm (e.g., the DSR, the AODV) of the current Ad-Hoc (point-to-point network), the following steps need to be implemented:
when needing to send data, a terminal A initiates a routing discovery flow, that is, sends a broadcast to all accessible UEs and inquires whether there is an available routing path accessing to a terminal B.
1. If the UE (e.g., UE D) receiving a routing discovery data packet does not have the available path accessing to the terminal B, it can forward the broadcast as well until the usable path accessing to the B is found; and
2. if the UE (e.g., UE E) receiving the routing discovery data packet has the available path accessing to the terminal B, the terminal feeds back a reply message so as to establish a path from the A to the B.
If according to the “active routing protocol algorithm” of the current Ad-Hoc, each node periodically transmits a local routing table to neighboring nodes, or transmits the routing information thereof to the neighboring nodes, when the routing table thereof changes.
No matter which aforementioned routing algorithm is adopted, due to massive invalid broadcasts generated during the routing discovery broadcast process, a larger signaling cost burden will be caused. Moreover, the process is unlikely to converge, and thus a larger delay will be generated in the entire process of path selection.
Therefore, a novel technical solution is needed to avoid massive signaling overheads caused by flooding routing in the existing routing algorithms, reduce unnecessary signaling overheads caused by broadcast in an overlarge range when the topological structure is established, and improve the timeliness of a database of the topological structure.